Uroplakin III is found in the inner membrane of the urinary bladder and contributes to the strength of that membrane and to the membrane's ability to stretch when the bladder is full. Uroplakin III can be expressed in primary and invasive bladder epithelial carcinomas, but is not expressed in many non-urothelial tumors, thus contributing to the research of bladder epithelial carcinoma. The Uroplakin III gene is deleted in normal urothelium and in bladder cancer after malignant metastasis, which can manifest as urothelial tumors with malignant tendencies and can be used as a reference for cell differentiation of urothelial cells. Uroplakin III-positive bladder epithelial cancer patients have a high relative survival rate.